[unreadable] The long term objective of this research application is to develop an integrated ultrasound and digital x-ray imaging system for screening and diagnostic mammography. Our primary hypothesis is that the simultaneous acquisition, and presentation of spatially correlated digital x-ray and ultrasound images of the breast will improve the inherent sensitivity and specificity of conventional screening mammography, particularly for patients with dense breasts, leading to a substantial reduction in missed cancers and unnecessary biopsies. A secondary hypothesis is that the proposed computerized acquisition of full-breast ultrasound images will decrease the operator-dependent variability of conventional free-hand breast sonography. Specific aims of Phase I research are to: (1) Develop a prototype integrated system designed to simultaneously acquire optimized breast ultrasound and digital mammography images; (2) Compare the imaging performance of the integrated system to the imaging performance of conventional dedicated breast ultrasound and full-field digital mammography systems; and (3) Develop and evaluate methods for spatial registration and display of simultaneously acquired breast ultrasound and digital mammography images. Phase I research will focus primarily on feasibility studies, utilizing ultrasound, x-ray and multi-modality breast phantoms to evaluate the performance of the integrated system over a limited field-of-view. Phase I research results will be used to develop several full-breast clinical prototypes in Phase II and to test the clinical outcome hypothesis indicated above. [unreadable] [unreadable]